12-core Mac Pro - 6 x 4GB vs. 3 x 8GB?

Discussion in 'Mac Pro' started by bluesteel, Oct 22, 2010.

  1. bluesteel macrumors 6502

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    #1
    taking into consideration that i want to enable triple channel memory mode, with about 24GB of RAM, and desire the most optimal performance out of my Mac Pro, which configuration would give me better performance on a 2010 12-core Mac Pro; 6 x 4GB modules (first three slots in both trays), or 3 x 8GB modules (first three slots in one tray)?

    is there improved performance by using the first three slots in both trays over the first three slots in just one tray?

    other than the capacity to have more space for additional memory, is there any other advantage to 8GB RAM modules versus 4GB modules?

    i'll be working with 3D animation and visual effects. thanks for looking :)
     
  2. poot1234 macrumors member

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    #2
    It doesn't matter in terms of performance.

    Remember though, if you get the 3x sticks now, you can upgrade to more down the road.
     
  3. bluesteel thread starter macrumors 6502

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    #3
    thanks for the advice :)

    if i get 6 x 4GB, i can expand up to 40GB in the future. but then i would lose the triple channel mode, right, if i were to have 6 x 4GB and then add 2 x8GB in the future?

    i can't think of a scenario where i will ever need more than 32GB of RAM. plus, with OWC RAM, the RAM i normally buy, there is a $300 difference between 24GB (6 x 4GB) and 24GB (3 x 8GB). considering the price difference, would you go with 3 x 8GB anyway?
     
  4. poot1234 macrumors member

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    #4
    If you truly think that it's work the extra money to have the peace of mind of knowing that you'll be able to upgrade in the future, go right ahead. If you don't plan on updating soon, I'd go with the 6x 4gb. And yes, you'd lose triple channel mode if you had anything but 3 or 6, etc.
     
  5. alust2013 macrumors 601

    alust2013

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    #5
    Actually, that's not true. There is a slight (probably not noticeable though) increase when you have triple channel for each processor. If you have all the memory one one CPU, the other has to go through it to get to what is there, which takes longer. This is still pretty fast, so I don't think you have reason to worry with either way you go. My suggestion is that if you don't think you'll need more than 32, just get 6x4GB. Probably cheaper that way too.
     
  6. jav6454 macrumors P6

    jav6454

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    #6
    Has to be n by 4GB modules, seeing as how we don't even have 8GB RAM sticks as of yet.
     
  7. alust2013 macrumors 601

    alust2013

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    #7
    Check this out. Probably not the best, I think OWC has a better selection, but they are out there.
     
  8. jav6454 macrumors P6

    jav6454

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    #8
    So crammed! Latency at 9?! I wouldn't touch it with a 10ft pole.
     
  9. bluesteel thread starter macrumors 6502

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    #9
    this is why i asked actually. i thought i had read somewhere in the past month about this exact same scenario. i'm pretty sure your right. i wonder if this makes a difference when rendering a heavy maya scene.
     
  10. Transporteur macrumors 68030

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    #10
    The difference between CL7 and CL9 is practically non-existent.
    You may be able to tell a minimal difference with synthetic benchmarks, in real world applications, however, there is no difference whatsoever.
     
  11. Bubba Satori Suspended

    Bubba Satori

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    #11
    Yep.
     
  12. vogelhausdesign macrumors regular

    vogelhausdesign

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    #12
  13. philipma1957 macrumors 603

    philipma1957

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  14. nanofrog macrumors G4

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    #14
    Yes, but the OEM memory is CL7 IIRC, and I'm not sure how the firmware would handle CL9 (may work, may not, as it may not include the full SPD timings - that is, limited to CL7, but will be able to allow 1333 to work if the CPU supports it, or 1066 otherwise).

    We need a guinea pig... er.... test subject to find out (ideally, test CL 9 in ECC and non ECC RAM varieties). :D :p
     
  15. Transporteur macrumors 68030

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    #15
    Are you sure about CL7 for the 2010 Pro's?
    The 1066MHz RAM in my 2009 machine indeed is CL7, I haven't seen any 1333MHz CL7 yet, though.

    When I look for 1333 ECC, all of them seem to be CL9.
     
  16. nanofrog macrumors G4

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    #16
    1333 comes in CL7, CL8, CL9, and CL10 varieties (CL7 = fastest of the JEDEC standard modules). CL9 is the most common I've seen as well.

    If CL9 works, great, as CL7 will be harder to find, and more expensive (and most won't be able to tell the difference IMO). I just seemed to recall spotting an Apple page that stated CL7 for both 1066 and 1333.
     
  17. aquablue macrumors member

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    #17
    Is the OWC 8GB 1333 RAM CL9?

    Also, does anybody know if 8GB sticks are working properly in the new MP without issues even though they are unsupported by apple?
     
  18. nanofrog macrumors G4

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    #18
    I took a look at OWC's page, and it is CL9 (UDIMM = 1, 2, and 4GB sticks & RDIMM = 8GB sticks). :) So apparently Apple didn't limit the timings. :D

    Good news IMO, as it will open up the ability to use other commonly available RAM, so long as it meets the rest of the specifications.
     
  19. bluesteel thread starter macrumors 6502

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    #19
    OWC 8GB sticks work fine in the 2010 Mac Pro, they have been testing them for a while. I guess you can't mix the 8GB sticks with 1GB, 2GB, or 4GB chips, though....from what i've read.
     
  20. Transporteur macrumors 68030

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    #20
    Really? Mixing 1, 2 and 4GB sticks worked at least in the previous Mac Pro.

    Is there any reason why mixing these with 8GB sticks shouldn't work? :confused:

    Would be a total bummer for people who don't wanna jump on the 8GB train overall.
     
  21. alust2013 macrumors 601

    alust2013

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    #21
    I believe it is due to the density of the modules
     
  22. nanofrog macrumors G4

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    #22
    Yes.

    You cannot mix different types of DDR3.

    There's non-ECC, and 2x forms of ECC; UDIMM (U = Unbuffered) and RDIMM (R= Registered). There's even differences that you cannot mix the 4GB with 1 or 2GB sticks due to the thermal sensors, according to OWC (presume the lack of thermal sensors on the smaller sticks, as they won't get hot enough to need them = cost savings).

    So you have to keep it all the same; 1 - 2GB UDIMM's (mixable), 4GB UDIMM's only, 8GB RDIMM's only, or all non-ECC DDR3 only (typical DDR3 desktop memory).

    Hope this helps. :)
     
  23. Transporteur macrumors 68030

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    #23
    Wait a second, that means that I can't even put 4GB sticks (assuming they would be the same type as the existing ones) in my Pro which currently uses 2GB sticks?

    Wow! Bummer!

    I always thought that was possible.
     
  24. nanofrog macrumors G4

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    #24
    Not according to OWC. :(

    The only thing that makes sense to me (as 1,2, and 4GB sticks are UDIMM), is that the smaller capacity sticks (1 & 2GB) don't have the thermal diodes on them (make sense from a production cost POV, as the smaller capacity DIMM's won't need them).

    Sucks, but it's the most logical explaination.
     
  25. Transporteur macrumors 68030

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    #25
    Well, glad that we talked about that as I'm constantly looking for a good deal on two 4GB sticks. I think my search is done. :p Thanks for the heads up!

    Why exactly do the smaller sticks not need a thermal diode?

    AFAIK the Hynix memory my Pro uses (Apple supplied RAM) has thermal sensors, at least iStat menus reads them. Actually, I thought that RAM that is supposed to work in a Pro requires thermal sensors (reason being the SMC).
     

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